JavaProgramming_SlideNotes1
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Transcript of JavaProgramming_SlideNotes1
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CAREER ENTRY COURSE FOR SOFTWARE DEVELOPERS - JAVA
JAVA
PROGRAMMINGLANGUAGE
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Simple Input/OutputOperation
Objectives Simple Input Command
Character
String
Simple Output Command
Convert String to
Integer Real
Programming Exercises
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Simple Input Command
The form of input can be keyboardentry from the user.
Values input by user can be numerical
or non-numerial. Java has some standard input
commands that allows the user to usethe commands to input values via thekeyboard.
We shall look at the character andString input
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Character Input Command
Characters are read from the keyboardusing System.in.read() method.
One of Javas console function.
Accepts input from the keyboard.
in object has access to method read()which retrieves data from keyboard.
The main() method header had aphrase throws Exception added at theend of the line.
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Character Input Command
Exception is an error situation, bythrowing the exception, thecompiler will handle the differentsorts of errors.
Programs accepting input fromkeyboard will not be able to
compile successfully without thephrase throws Exception.
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String Input Command
TheInputStreamReader() is used toread characters from the keyboard.
The BufferedReader() is used, for it
provides the readLine() methodtoallow programs to read from keyboarda line at a time.
Java implements I/O operationsthrough streams.
Represented by two abstract classes,InputStream and OutputStream.
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String Input Command
These are found injava.iopackage.
Thus, have to import this packageinto the program, which is placeat the beginning of the program.
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Simple Output Command
System.outis a PrintStream object thatallows output to be displayed.
Two methods used, i.e.print() and
println() method. print() method allows the cursor to be
positioned on the next availableposition on the same line.
println() method allows the cursor tobe positioned on the next line.
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Convert String to Integer
Converts String containingnumbers to numerical data toperform arithmetic calculation.
Use teIntegerclass, which is partof thejava.lang package.
parseInt() method from the
Integerclass is used to convertString to integer.
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Convert String to Real
Use the Double class, which ispart of thejava.lang package.
parseDouble() method from theDouble class is used to convertString to real numbers.
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Programming Exercises
Q1) Write a Java program to capture theusers name and age and displays thename and converts the age to aninteger and displays the age with ameaningful message.
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Control Structures
Objectives To write Selection statements
To write Iteration statements
Programming Exercises
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Selection Statements
Based on the user input, decision making willtake place.
It involves choosing between two alternativecourses of action.
Java supports two kinds of selection statements
The if, if..else or nested ifstatement
Theswitch statement
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Selection Statements
The ifstructure
A single-alternate ifas it only performs anaction based on one alternative.
The if..else structure A dual-alternate ifas it requires two
options for the next course of action.
Performs one action when a booleanexpression evaluates as true and another
when the boolean expression evaluates asfalse.
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Selection Statements
The Nested ifstructure
An ifwithin another ifstatement.
Nested ifstatements are useful
when two conditions must be metbefore some action is taken.
Theswitch structure
Another alternative for nested if
statements. Useful when testing single variable
against a series of exact integer orcharacter values.
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Example ofif statement#1
class SampleIf{
public static void main(String[] test) {
int number = 5;
if(number > 0){
System.out.println(The number is positive.);
}
else
System.out.println(The number is negative.);
}}
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Example ofif statement#2
class SampleIf {
public static void main(String args[]) {
System.out.print("Hello ");
System.out.println(args.length);
if (args.length > 0) {
System.out.println(args[0]); }
if (args.length
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Example ofswitchstatement
class SampleIf {
public static void main(String args[]) throwsException {
char ans , upans ;
System.out.println("Enter A or B ");ans = (char) System.in.read();
upans = Character.toUpperCase(ans);
switch (upans) {
case 'A :System.out.println(" First option");
break;
case 'B :System.out.println(" Second option");
break; }
} }
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Iteration Statements
A structure that allows a block of statementsto be executed repeatedly depending on theevaluation of the boolean expression.
A loop that never ends is called an endless loop
or infinite loop.
A loop within a loop is called a nested loop.
Java supports three kinds of iterationstatements
The while loop The do..while loop
The forloop
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Iteration Statements
The while loop
Used to repeat a statement or block only ifthe condition is true.
The do..while loop
Used when we need to execute the loopbody at least once before checking thecondition.
like the while loop, it will only repeat astatement or block if the condition is true.
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Iteration Statements
The testing of the condition is placed differently
while loop test the condition first, thenexecute the body of statements.
do.. while execute the body of statementsbefore testing the condition.
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Example ofwhile loop #1class SampleWhile{public static void main(String[] test) {
int count = 1;
System.out.println(Good Day!);while (count
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Example ofwhile loop #2
class SampleWhile{
public static void main(String[] test) {
int num = 1;
while (num < 5) {System.out.print(num*2);
num = num + 1;
}
}
}
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Example ofdo-while loop #1
class SampleDoWhile{public static void main(String[] test) {
int count = 1;
System.out.println(Good Day!);do {System.out.print(INFORMATICS);count = count + 1;
} while (count
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Example ofdo-while loop #2
class SampleDoWhile{
public static void main(String[] test) {
int num = 1;
do {System.out.print(num*2);
num = num + 1;
} while (num < 5) ;
}
}
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Iteration Statements
The forloop
Allows the statements in the loop body tobe executed a specific number of times.
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Example offor loop #1
class SampleFor{
public static void main(String[] test) {
System.out.println(Good Day!);
for(int count = 1; count
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Example offor loop #2class SampleFor {public static void main(String[] test) {
System.out.println(ASCII");
for (int count = 0 ; count
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Example offor loop #3class SampleFor {
public static void main(String[] test) {
System.out.println("Graphics ");
for (int x = 1; x
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Programming Exercises
Write a Java program to capture the users nameand age
and display a message based on the followinginformation:
if age > 65 display retired
if age is between 22 to 65 display working
if age is between 7 to 21 display studying
if age < 7 display playing
The user will be prompted to enter another nameand age.
If the user decides not to enter another name, the
program will terminate.